上传文件至 'w6'

w6/Animal.java

@@ -0,0 +1,3 @@
+public abstract class Animal {
+    public abstract void makeSound ();
+}

w6/Cat.java

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+public class Cat extends Animal{
+    @Override
+    public void makeSound() {
+        System.out.println("猫：喵喵喵");
+    }
+}

w6/Dog.java

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+public class Dog extends Animal implements Swimmable{
+    @Override
+    public void makeSound() {
+        System.out.println("狗：汪汪汪");
+    }
+
+    @Override
+    public void swim() {
+        System.out.println("狗会游泳");
+    }
+}

w6/Main.java

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+public class Main {
+    public static void main(String[] args){
+        Animal dog = new Dog();
+        Animal cat = new Cat();
+
+        System.out.println("动物叫声");
+        dog.makeSound();
+        cat.makeSound();
+
+        System.out.println("是否会游泳");
+        if (dog instanceof Swimmable){
+            ((Swimmable) dog).swim();
+        }
+        if (cat instanceof Swimmable){
+            ((Swimmable) cat).swim();
+        } else {
+            System.out.println("猫不会游泳");
+        }
+    }
+}

w6/Swimmable.java

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+public interface Swimmable {
+    void swim();
+}